<hr><i>drh added on 2010-02-10 13:20:00:</i><br>
The ] and [ characters are also legal for Unix filenames.  (Any character 
other than 0x00 and / is valid in a unix filename.)  But ] and [ are used
as globbing characters by the shell, so there use must be escaped in the shell.
this can lead to subtle problems.  So as a safety mechanism, I deliberately
disallow such filename characters in Fossil.

Behavior is by design.